Process for treating hydrocarbons



Patented Nov. 12, 1946 rnoonss non TREATING HYDROCARBONS Orris L. Davis and Alan C. Nixon, Oakland, Calif., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware NoDi-awing. ApplicationOctober 27, 1943, Serial No. 508,089-

13 Claims. 1

This invention deals withe, method for improving the rate of separation of aqueous alkaline treating solutions or solutions from hydrocarbons or of facilitating steam stripping of the resulting fat alkaline solution, if the latter isdesired, or both.

It is well known that hydrocarbon oils are mixtures of hydrocarbon and may contain compounds of many different degrees of saturation, suchas parafiins, olefins, polyolefins, acetylenes, naphthenes, or aromatics. It is also known that hydrocarbon oils frequently contain weak acids e. g. having dissociation constants below about 10- such as hydrogen sulfide, mercaptans, alkyl phenols, etc. It is. often desirable to treat such hydrocarbon mixtures to separate them into hydrocarbons of different degrees of saturation, or to purify particular hydrocarbons, such as benzene, toluene, xylene, butylenes, butadiene, isoprene, ethylene, acetylene, etc.; or to remove weak acids of the type mentioned above from such hydrocarbons or mixtures.

One method of carrying out such a separation or purification is by extracting one or more of the components with an alkaline. solution, which has a preferential solvent power for one or more of the components of the mixture, and thereafter separating the resulting alkaline solution from the dissolved portion of the mixture. The extraction may be either by liquid-liquid or by vapor-liquid contact, including extractive distillation. (In order to achieve separation by extractive distillation the two or more compounds to be separated from one another should as a rule boil not more than about 20 C. apart and prefer-- ably not more than about C. apart.) These extractions are normally carried'out in apparatus permitting contact of the alkaline treating solution and the mixture containing the hydrocarbons, usually by counter-current flow, either through a packed or a plate column, or through a series of mixers and settlers, whereby two end, phases are produced and separated, one of which is an extract comprising the fat alkaline treating solution containing the extracted portion of the mixture, and the other of which is the rafiinate portion of the mixture. These two phases may be both liquid or one may be liquid and the other may be a vapor. For reasons of economy, the fat alkaline solution is usually regenerated such as by steam stripping, air blowing or washing with a suitable wash liquid, etc., and the regenerated solution is then re-used for treatment of further quantities of the original mixture.

The mixtures to which this invention, is applicable are either normally liquid or normally gaseous and preferably have an end boiling point of below about, 200 C. They are comprised of hydrocarbons and must be substantially free from sulfate ester acids, sulfonic acids, or other relatively strong acids because of the effect of these acids upon the alkaline treating solution by permanently poisoning or neutralizing it.

Aqueous alkaline treating solutions which may be employed must be stable and inert so as not to react irreversably with the components of. the mixture under the conditions of the process; they must have a greater solvent power for some components than for others; and they must be separable from the dissolved components by physical means such as, by fractional distillation and/or washing-out, either while they are in the form originally absorbed or else after they have been changed chemically by a simple operation such as air oxidation. If employed in, liquid extraction, they must be only partially miscible with mixtures to be extracted.

Some specific examples of alkaline treating solutions for the separation of unsaturated hydrocarbons from mixtures containing them are: solutions of complex compounds of ammonia and salts of univalent heavy metals from groups I and II of the periodic table, such as copper, silver, gold, mercury, etc., chlorides, nitrates, cyanides, acetates, etc., in water. In the extraction of weak acids normally associated with petroleum oils, alkaline treating solutions, such as tripotas slum phosphate, sodium phenolate, sodium borate, sodium or potassium carbonate, etc., or strong solutions of alkaline metal hydroxides, preferably having concentrations. of 25 to or alkaline solutions containing solutizers may be employed.

Solutizers are known as organic substances which when in the liquid state are solvents for weak. organic acids, are substantially insoluble in water-immiscible liquids, are soluble in aqueous strong bases, are chemically inert to the action of said bases. even at. elevated temperatures, and have boiling temperatures preferably substantially higher than water. Solutizers are used to enhance the extractive powers of aqueous alkaline solutions for weak organic acids such as mercaptans and phenols. The solutizer process and the various solutizers have been described in a series of patents and patent applications as well as in the general literature, for example, in the Yabrofl et al. U. S- Patents 2,149.3.79,

2,149,380,, 2,152,166, 2,152,720, 2,152,723, 2,164,85 2,186,398, 2,202,039; applications Serial Numbers 3 255,684, filed February 10, 1939; 271,962, filed May 5, 1939; Refiner and Natural Gasoline Manufacture, May 1939, pages 171-176, and March 1940, pages '73-'76, Industrial Engineering and Chemistry, volume 32, pages 257-262, February 1940, etc.

In choosing one of the above alkaline treating solutions, sight must not be lost of the boiling temperature requirements relative to the boiling temperature of the mixtures. in vapor-liquid extraction, it is important that the solvent chosen have a boiling temperature higher than that of the mixture to be treated, and in the specific case of extractive distillation, it is desirable that the boiling temperature of the solvent be not less than about 50 higher than the boiling temperature of the mixture. Accordingly, the particular treating agent to be employed necessarily depends upon both the boiling temperature of the mixture to be treated, and the type of process to be used in the treatment.

Unfortunately, processes of this type often produce foam and/or emulsions which greatly reduce the maximum throughput of a given treating unit. Emulsions, if formed, occur in liquid-liquid treating, and foaming may occur in vapor-liquid treating. Foaming may also occur if distillation,steam stripping, air blowing, etc., is employed as a means for recovering the alkaline treating solution from the extract or raffinate.

The nature of the substances responsible for difficulties is not definitely established. It is believed, though, that foam and, emulsion are produced by small amounts of impurities, such as compounds related to gasoline gums or similar resinous materials formed by reaction of some of the components of the hydrocarbon mixtures with themselves or with the alkaline treating solution or a component thereof, particularly in the presence of oxygen. In many cases it is impossible to keep air away from such mixtures, since small quantities easily leak through joints of pumps and valves, etc. Thus, most hydrocarbon oils contain small but definite amounts of dissolved oxygen. In the case of treating solutizer solutions with alkaline solutions containing phenolates, a phenol type resin may be formed, for instance, by the interaction of mercaptans, aldehydes or other impurities in the mixture treated.

Accordingly, it is the purpose of this invention to provide means for improving the rate of separation of aqueous alkaline treating solutions from the hydrocarbons which are being treated. Another purpose is simultaneously or independently to reduce the foaming tendency of the treating solution, for example, when it is being regenerated by steam stripping. Still another purpose is to provide means for preventing the formation of emulsions caused by the presence of emulsifiers in the treating liquids, particularly those containing impurities which readily react to form emulsifiers. It is yet another purpose to provide a remedy for breaking emulsions formed in such treating processes.

It has been discovered that the addition of relatively small amounts of a stable organic surfaceactive agent which contains at least 8 carbon atoms per molecule and has a molecular weight of below about 1000 (preferably below about 600) and which is soluble in, or spontaneously forms, a colloidal dispersion in the alkaline treating solution, results not only in reducing foaming and in an improved rate of separation, but also in effective and rapid breaking of emulsions which may form between the two phases produced in the process. The term surface-active agent For example,

as herein used refers to substances which are capable of doing work at the interfaces, i, e., produce a marked change in interfacial tensions. It is important that the agent be readily and completely dispersed through the treating solution so as to be continuously and evenly effective throughout the entire zone of contact.

The agents should be reasonably stable toward the action of oxygen in the presence of caustic alkali and at elevated temperatures of steaming if steam regeneration is employed as part of the process.

In a regenerative process wherein the spent treated solution is continuously regenerated and recirculated for further contact with the mixture to be treated, it is desirable but not essential, that the surface-active agents, in order to be more or less permanently useful, should not be extracted from the treating solution when the latter is contacted with the hydrocarbon mixture. The presence of the agent in either of the separated components of the mixture may be undesirable, as it may interfere with their intended uses.

In some cases, it may be desirable to remove these agents from the treating solution in which case they should have a property which makes possible such separation.

The organic surface-active agents of this invention are anion active and cation active compounds. These are organic compounds containing at least one atom of oxygen and/0r nitrogen; aliphatic alcohols having between 8 and 14 carbon atoms per molecule; and primary, secondary and tertiary organic amines having more than 8 carbon atoms and an alkyl radical of not less than 4 carbon atoms, such as lauryl amine, alkyl pyridines and quinolines, etc. Such surface-active compounds may be generally represented by the formula RY, wherein R is an organic radical and Y is a polar radical containing an atom selected from the group consisting of oxygen and nitrogen.

Those which are more effective for breaking and reducing foams are the alcohols having from 8 to 14 carbon atoms such as octyl, monoyl, decyl, undecyl, dodecyl, etc., alcohols. Alcohols containing less than 8 carbon atoms per molecule such as isoamyl alcohol and n-hexyl alcohol and those containing more than 14 carbon atoms such as cetyl alcohol are substantially ineffective for the described purpose.

Amounts of the surface-active agents which need to be added to improve the rate of settling or breaking of the emulsion or foam or both, are insufiicient to materially affect the action of the treating agent. This amount may vary between about .001% and 1%, and preferably between about .001% and .1% by volume of the treating agent. The different types of treating agents are capable of dissolving different amounts of the surface-active agents and different mixtures may require different amounts .to reduce foaming and/or emulsification. This is probably due to the difference in reactivity of the ions of the re spective agents and their effect on the hydrocarbon mixtures treated. Therefore, actual laboratory tests Within the above limitation may be required to accurately determine the amount of the agent or combination of agents for the most effective separation of the given mixture witha given alkaline treating solution.

It is desirable that the beneficial effect of the agent shall not be restricted to and be dependent on a specific range of concentration substantially narrower than the limits indicated above-that is Example In the table below, effects of a number of representative surface-active agents are shown in 5. The process of claim 1, wherein the treating process is a vapor-liquid phase separation process.

6. The process of claim 1, wherein the surfaceactive agent is a cation-active agent.

'7. The process of claim 1, wherein said mixture contains diolefins and said alkaline treating solution is an aqueou alkaline copper ammonium acetate solution.

8. The process of claim 1, wherein the amount of the said surface-active agent is between about .0001% and 1% by volume of said mixture.

9. The process of claim 1, wherein the amount of the said surface-active agent is between about a spent or contaminated aqueous copper am- .001% and .1% by volume of said mixture. monium acetate solution which when fresh had he process o Claim wherein sa d disthe following composition: .25 mol/liter of cupric persion is a foam. ions, 2.93 mols/liter of cuprous ions, 10.4 11. In a process for treating a hydrocarbon mols/liter of ammonia, and 4.0 mols/liter of fraction with an aqueous copper ammonium aceacetic acid. Samples of this spent solution were tate solution, whereby two phases are produced, subjected to an emulsion test in which they were in which .process a relatively stable dispersion of agitated with an equal amount by volume of terone phase in the other is produced by the action tiary amylenes at a temperature of about F. of impurities formed as a result of reactions of The resulting emulsion was then allowed to settle unsaturates in said mixture with each other and and the time required for substantially complete 25 with O ygen, the method of preventi h a separation was noted and whether or not at the dispersion which comprises effecting said treatend of .the settling a residual rag (large globules ing in the presence of a relatively small amount of hydrocarbon surrounded .by thin films of soluof an organic amine having at least one alkyl tion) was left at the interface between the solvent radical of more than 4 carbon atoms miscible in phase and the hydrocarbon phase. The results said aqueous copper ammonium acetate solution. were as follows: 12. In a process for purifying a hydrocarbon Gone. in Settling Vol. of Organic surface-active agent gm./l00 cc. time in residual Remarks solvent minutes rag Fresh solution 0 1% 0 Nofoam. Spent solution 0 9 Stable foam.

I. Alcohols:

Decyl alcohol .3: .1 30 1 N0 foam Do .01 30 1 D0. Do 0025 Do. Act best as defoamers. Lauryl alcohol--- .01 12 10 Light foam 2-ethyl hexanol .1 l5 10 No foam II. Amines:

Lam-y] amirm ,1 M 4 N0 foam. Amine ester of fatty acid 1 3 0 Do. Do .0l 3% 0 Do. Fatty acid salt of substituted oxazoline :5 3g 8 B8:

We claim as our invention:

1. In a process for treating a mixture comprising hydrocarbons with an aqueous alkaline treating solution of a compound selected from the group consisting of alkaline alkali metal compounds and alkaline ammonia compounds whereby two phases are produced, in which process a relatively stable dispersion of one phase in the other is produced by the action of impurities formed as a result of reactions of components of said mixture, the method of reducing the stability of such a dispersion which comprises effecting said treating in the presence of a relatively small amount not more than about 1% by volume of said mixture of an organic surface-active agent having at least 8 carbon atoms per molecule and a molecular weight below about 1000, said agent being soluble or spontaneously dispersible colloidally in said aqueous'treating solution and substantially insoluble in said mixture, and being an organic amine having at least one alkyl radical of more than 4 carbon atoms.

2. The process of claim 1, wherein said mixture is a gasoline distillate.

3. The process of claim 1, wherein said mixture contains C4 diolefins.

4. The process of claim 1, wherein said treating process is a liquid-liquid phase separation process.

mixture containing a C4 diolefin by liquid-liquid phase treatment with an aqueous alkaline solution of a complex compound of ammonia with a copper salt, whereby two phases are produced, in which process a relatively stable dispersion of one phase in the other is produced by the action of impurities formed as a result of reactions of components of said mixture, the method of reducing the stability of such a dispersion which comprises eifecting said treating in the presence of between about 0.0001% and 1% by volume of said mixture of a fatty acid ester of an amine containing an alkyl radical of more than 4 carbon atoms.

13. In a process for treating a hydrocarbon fraction with an aqueous copper ammonium acetate solution, whereby two phases are produced, inwhich process a relatively stable dispersion of one phase in the other is produced by the action of impurities formed as a result of reactions of unsaturates in said mixture with each other and with oxygen, the method of preventing such a dispersion which comprises eifecting said treating in the presence of between about 0.0001% and of an organic amine having a molecular weight of not more than 600 and having an alkyl radical of more than 4 carbon atoms.

ORRIS L. DAVIS. ALAN C. NIXON. 

